The word "contractor" is overloaded. Many folks, apparently including the Nintendo workers described [1], are actually not contractors, in the 1099 sense, under the law. Instead, they are W-2 employees of Company B, which is hired by Company A. Company B is legally responsible for offering them benefits, but they don't have to be equal to Company A's.
[1] "The specific charge, as first reported by Axios, is levied against both Nintendo of America and recruiting firm Aston Carter, which hires contractors for various administrative and customer support roles at Nintendo." https://www.ign.com/articles/former-nintendo-employee-accuse...